Product Description RespoKare Anti-Pollution Mask Adult (Small Size Wide 14 cm.): 1  piece (1 piece/pack)   Features Composed of filter 5 layers Particulates filter 0.3 micron or PM2.5 > 95% Active Respo Layer driven by U.S Technology Neutralizes of NO2, S02 and Toxic Gases > 90% Reusable unless soiled or damaged Stick-on Pollution Indicator signals when to replace the Mask How It works RK Anti-Pollution Mask is the only mask which both filters particulates like PM2.5 and neutralizes toxic gases including Nitrogen Dioxide (NO2) and Sulfur Dioxide (SO2),enables you to brave outdoor activities amid air pollution without a second thought.The Active Respo Layer protects you by neutralizing up to 90% Nitrogen Dioxide (NO2), Sulfur Dioxide (SO2) and other pollutants. Long Lasting Active Protection RespoKare Anti-Pollution Mask with Active Respo Layer Design is the only mask capable of neutralizing toxic gases including Nitrogen Dioxide (NO2) and Sulfer Dioxide (SO2), as well as filter particulates such as PM2.5. Providing up to 8 hours of protection upon removal from packaging, the mask is suitable for everyday use in polluted urban environments. RespoKare Pollution Indicator Each mask comes with a proprietary stick-on Pollution Indicator to signal when to replace the mask. Once stuck onto the mask, the indicator gradually changes color from natural off-white to dark brown after exposure to toxic gases. It is recommended that users replace the mask when the Pollution Indicator reaches a dark brown colour, even if the duration of wear is under 8 hours.